One method currently used to address environmental concerns for conventional disposable food container products is the manufacture of starch-based disposable food service items such as trays, plates, and bowls. Because starch-based biodegradable food service items are formed in heated molds, much or all of the starch in these items is cooked, and cooked starch is sensitive to moisture. When exposed to water, other aqueous fluids, or significant amounts of water vapor, these items may become very soft, losing form-stability and becoming susceptible to puncture. The moisture sensitivity of these items can be a drawback in some applications, particularly more demanding, high moisture applications such as ready to eat meals, bakery items, frozen ready meals, chilled food, soup and noodle bowls, cups for coffee, hot chocolate, and other beverages, cereal bowls, ice cream and yogurt cups, and other similar high-moisture applications. On the other hand, such starch based products are desirable in that they can withstand higher temperatures, which makes them desirable as containers for many of the aforementioned applications, and they are readily compostable.
Another property that may be desirable for certain packaging applications using starch-based items is good impermeability to oxygen or other gases. However, starch items are often permeable to oxygen and other gases, such that some modification of the starch composition and/or the item itself would be required to provide improved barrier properties.
Non-biodegradable and biodegradable films having acceptable moisture and oxygen resistance are known in the art. However, when laminated to biodegradable cardboard, paper or plastic materials to make them functional, these films adhere to the cardboard, paper or plastic substrates such that the biodegradable and non-biodegradable portions cannot be easily separated, effectively eliminating the environmental advantages of the biodegradable portion.
Accordingly, there is a need in the art for improved containers with increased moisture resistance, oxygen barrier or other gas barrier, with biodegradable and environmentally friendly properties that allow easy disposal of the various parts.